Cherri Gervais got her first gray hairs as a teenager. “It’s genetic,” she said. Her hair color, a striking shade of silver, is the first thing people on TikTok noticed when she asked them to tell her how old she looked in a recent video. Sign up for The Morning newsletter from the New York Times The guesses ranged wildly. Many were correct, or close enough, Gervais said. (She turned 34 this month.) Other suggested she was in her 60s or 70s. Gervais, who lives in Kansas and works for a part-time